Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System

Over-exploitation of groundwater in India’s fastest-growing metropolis, Bengaluru, has resulted wells being bored to unprecedented depths a crystalline-rock aquifer. However, key questions about sustainability this extraction process remain unaddressed due the complexity monitoring. Using primary surveys, study looks at spatio-temporal evolution on city scale, finding that catchments with deficient water infrastructure have deeper wells. To maintain yields, well >400 m are drilled, especially since 2000, leading unsustainable extraction. Camera inspections 54 Electronic City 2016 and 2017 revealed levels majority remained lower <100 m, although some had >250 m. Analysis δ18O δ2H signatures samples all followed local meteoric line indicating recent recharge, implying drilling only increases borehole volume does not tap into newer sources. Water may stabilize depths, subject high spatial variability, density drilling, connectivity upper zones. Given interconnectedness between shallow aquifers, our research shows increasing borewell could be good indicator for falling aquifer levels. This fills an important gap peri-urban, intermediate-scale conceptualizations across different land uses provides further evidence difficulties reliable monitoring over-exploited hard-rock aquifers Bengaluru city.